Synthesis and Stability of Lead-hydroxyapatite

Lead-hydroxyapatite was a new mineral phase of lead-bearing phosphate formed from the stabilization of fly ash treated by phosphate.The control conditions of the formation of various new phosphates from reaction between PO3-4 and lead ions(XPb) in terms of different molar ratios were studied.The products' characteristics,thermal behaviors and chemical stability were also discussed.It is indicated that Ca8Pb2(PO4)6(OH)2,Ca5.5Pb4.5(PO4)6(OH)2,Ca2.12Pb2.22(PO4)3(OH)0.67,Ca2Pb8(PO4)6(OH)2 and Pb10(PO4)6(OH)2 are synthesised respectively with the increase of XPb at the pH value of 10.And the products are changed from clavate polymer,granulated aggregate to massive aggregate.Furthermore,they can exist stably below 400℃.The lead leached via TCLP are decreased with the increase of the pH value of leaching solution.When the XPb is in the range from 0.1 to 0.7,the products perform good chemical stability.However,the stability is weakened when the XPb is above 0.7.